Vacuum cleaners can include an agitator for agitating debris on a surface to be cleaned so that the debris is more easily ingested into the vacuum cleaner. In some cases, the agitator comprises a motor-driven brushroll that rotates within a base or floor nozzle. Brushrolls typically have a generally cylindrical dowel with multiple bristle tufts extending radially from the dowel.
Common types of brushrolls include injection-molded or wooden dowels, and may be drilled with holes for tufting with bristles. The shapes for the injection-molded dowel can be limited by tooling constraints and by the desire to maintain rotational balance of the brushroll during operation. In order to produce parts from a simple two-part tool and in order to maintain a straight line of draw, the injection-molded dowel must be symmetrical about its central axis, resulting in a symmetrical bristle pattern. Four-part tools with moving slides can be used to produce more complex dowel shapes with features that are not in the line of draw, but these dowels too are typically symmetrical about their central axis in order to maintain rotational balance during operation. Dowels machined out of wood allow for different bristle patterns. One feature found on some wooden dowels is a bristle stiffener that is molded as a separate strip and slid into a machined channel in the wooden dowel adjacent to the tufting area.